textproduct: Quad Cities

KEY MESSAGES

- A seasonably strong system will bring the potential for severe thunderstorms on Wednesday. An Enhanced Risk (Level 3 of 5) of severe thunderstorms is in effect for areas south of Highway 30, with the remainder of the area under a Slight (Level 2 of 5) risk. A moderate risk ( level 4 of 5) is clipping our far southeast and eastern counties.

- Heavy rainfall is possible, especially over northern Illinois through Wednesday. Flash flooding will be a risk for areas that see repeated rounds of intense rainfall.

- After several quiet days, the active pattern will resume with heavy rain potential developing late in the weekend in zonal flow aloft.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 221 AM CDT Tue Jun 16 2026

A shortwave with a weak cold front will track through the area this morning, with lifting ahead of the front producing scattered showers. Currently these showers are along a line from [LOCATION TO LOCATION] and are expected to move east across the area for the next several hours. However, given dry low levels, these showers are producing light to no rainfall. As a result, expect little to no accumulations. However, subsidence within the showers may produce some gusty winds, with observations in northwest Iowa showing gusts of 25-35 kts. These showers will exit the area by 9 AM this morning with the front. Following frontal passage, another seasonably cool and dry day. Highs in the mid to upper 70s are expected, along with westerly winds of 15-20 mph. Deep mixing during the day will support gusts up to 25-30 mph.

Tuesday night, the story shifts to an approaching strong shortwave tracking across the Upper Midwest. Guidance has narrowed in on the low tracking across southern Minnesota, with the potential for an additional area of low pressure to develop across eastern Iowa. This system has impressive dynamics and kinematics for mid-June, with mid- and low-level wind speeds in the NAEFS 99th percentile for this time of year. A westerly 500 mb jet with a jet max over 65 kts will move in across eastern Nebraska and western Iowa late Tuesday night, reaching eastern Iowa by early Wednesday morning. At the same time, the LLJ will be angled from the southwest with speeds over 50 kts.

With this strong low level southwesterly flow ahead of the shortwave, ample moisture advection is expected along the warm conveyor belt. Guidance continues to show PWATs of 1.5- 2.0 feeding into the area overnight through the morning hours. This will lead to a noticeable increase in humidity as dewpoints reach into the mid 60s to low 70s after our recent bout of drier weather. As a result of this high moisture content, any showers and storms that occur will be capable of heavy rain. There is a scattered risk of flash flooding, namely for those areas that receive multiple rounds of storms. As a result, a Slight (Level 2 of 4) risk of flash flooding is in place.

Of greatest concern with this system, however, is the threat of severe weather. Shear and instability will not be difficult to come by in this dynamically charged environment, leading to an Enhanced (Level 3 of 5) risk across the southern half of the CWA and a Slight (Level 2 of 5) risk to the north. A Moderate (Level 4 of 5) risk is to our southeast across central Illinois. Two rounds of storms appear likely: first, a morning round along the WAA wing, followed by an afternoon round supported by frontal forcing. Some uncertainty, namely in the extent of morning convection and timing of frontal passage, give us a few scenarios:

Scenario 1: Morning showers and storms develop along the nose of the LLJ across northeast Iowa and move southeast. Limited instability overnight would help limit the severe threat during the morning hours. Once these showers and storms move out of the area, diurnal heating is able to occur prior to the front moving into the area. Storms initiate along the boundary mid-afternoon, with all severe hazards possible and move out of the area by early evening.

Scenario 2: The airmass is not able to recover following morning convection. This can happen in 2 ways: first, showers and storms in the morning persist into mid-afternoon, or secondly, the cold front advances faster than forecast. Both of these would result in the severe threat being displaced to our east.

Scenario 3: Moisture return overnight is not as strong as guidance suggests, limiting showers and storms during the morning hours. With moisture arriving later in the day, diurnal heating would occur as moisture feeds into the region. This would allow for the afternoon storms to not be impeded by morning convection. Once again, strong forcing along the front would support all severe hazards.

For all of these scenarios, an additional concern is a capped environment. 700 mb temperatures south of I-80 are forecast to be high, which could limit any convection across southeast Iowa and northeast Missouri. However, any storms that are able to develop would be able to take advantage of a primed environment.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 221 AM CDT Tue Jun 16 2026

Past Wednesday, the forecast looks to be calmer as we return to the background northwesterly flow behind the departing system. High pressure will slide in Thursday from the northwest. Pleasant temperatures will remain in place, but the active pattern looks to return as zonal flow develops over the Midwest by late in the weekend. This pattern is a typical MCS pattern where heavy rainfall would be favored by short waves passing through the zonal flow. High amounts of moisture are expected in this pattern, as well as a seasonal/typical wind threat with any zonal MCS pattern. WPC is already highlighting our region with several inches of rainfall in the the later weekend to early week next week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1159 PM CDT Mon Jun 15 2026

Clear skies and southwest winds will continue for several more hours overnight, before a cold front moves closer to the area, with a few scattered very light showers possible. These are unexpected to wet surfaces and reduce any visibility, but could offer a 20% chance of a lightning strike at some point between 08z and 12Z. AFter 12Z, winds will switch to northwest and be gusty around 18kts gusting to 26kts.

A period of LLWS remains forecast just ahead of the front in the 08z-12Z time frame tonight, were winds aloft will reach near 40 kts around 2kft up.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.